The present invention generally relates to cue signal recording circuits for magnetic recording and reproducing apparatuses, and more particularly to a cue signal recording circuit for a magnetic recording and reproducing apparatus which records a cue signal on a magnetic tape by an erase head at the start of a recording so that the beginning of a desired pre-recorded program on the magnetic tape can be found by reproducing the pre-recorded cue signal from the magnetic tape during a cue mode, which cue signal recording circuit has a simple construction and can be manufactured at a low cost.
In a magnetic recording and reproducing apparatus such as a video tape recorder (hereinafter simply referred to as a VTR), the operator often wishes to find the beginning of a desired pre-recorded program on a magnetic tape (hereinafter simply referred to as a tape) which is recorded with a plurality of programs. However, it will be too troublesome and time consuming to search for the beginning of the desired pre-recorded program while monitoring the reproduced picture as the tape is moved at a speed which is the same as the speed with which the programs were recorded on the tape at the time of the recording. But if a cue signal is recorded on the tape at the beginnings of the programs, it is possible to find the desired pre-recorded program within a short time period by detecting the pre-recorded cue signal as the tape is moved at a speed which is higher than the speed with which the programs were recorded on the tape. A VTR which records such a cue signal on the tape comprises a cue signal recording circuit. At the start of a recording, the cue signal recording circuit of the VTR records the cue signal on the tape by an erase head at the beginning of a program, and the beginning of the desired pre-recorded program is found by reproducing the pre-recorded cue signal from the tape during a cue mode. During a cue mode, the tape is moved in a forward direction (fast-forward cue mode) or a reverse direction (rewind cue mode) at a speed which is higher than the speed with which the programs are recorded on the tape.
As an example of a conventional cue signal recording circuit, there is a cue signal recording circuit generally comprising an erase signal generator, a cue signal generator, a coupling capacitor, and a switch. According to this conventional cue signal recording circuit, the erase signal generator generates an erase signal having a frequency of 70 kHz, for example, and supplies the erase signal to a first input terminal of the switch. The cue signal generator generates a cue signal having a frequency of 30 Hz, for example, and supplies the cue signal to a second input terminal of the switch through the coupling capacitor. The switching of the switch is controlled responsive to a control signal applied to a third input terminal of the switch. The control signal is generated in a control signal generating circuit which is responsive to an output of a recording start button which is manipulated at the start of the recording. For example, the control signal controls the switch so that the switch selectively passes the cue signal supplied to the second input terminal thereof for approximately one second and thereafter passes the erase signal supplied to the first input terminal thereof. The output of the switch is supplied to an erase head. Since the erase head is supplied with the cue signal for approximately one second from the start of the recording and is thereafter supplied with the erase signal, the erase head records the cue signal on the tape for approximately one second from the start of the recording and thereafter erases pre-recorded signals on the tape. According to the conventional cue signal recording circuit, the cue signal is recorded on the tape at the beginning of each of the programs, and for this reason, it is possible to find the beginning of the pre-recorded programs by reproducing the pre-recorded cue signal from the tape during the fast-forward cue mode or the rewind cue mode of the VTR.
However, the erase signal generated by the erase signal generator of the conventional cue signal recording circuit, is a signal having a large level of 50 volts peak-to-peak, for example. Accordingly, a simple semiconductor electronic switch cannot be used for the switch which selectively passes the erase signal or the cue signal, and it is necessary to use a relay switch for this switch. In addition, the coupling capacitor must have a large capacitance in the order of 47 .mu.F, for example, because the cue signal generated by the cue signal generator has a low frequency. Further, the conventional cue signal recording circuit is disadvantageous in that the circuit construction is complex due to the provision of the erase signal generator and the cue signal generator which are completely independent circuits.